Support is requested from the Shared Instrumentation Grant Program to purchase a quadrupole mass spectrometer and high-pressure liquid chromatograph (HPLC) equipped with Electrospray Ionization (ESI) and Atmospheric Pressure Chemical Ionization (APCI) sources. The target instrument, a Finnigan LCQ, will be housed in the Instruments Facility, a shared core resource for major instrumentation located in the Department of Chemistry. The proposed ESI/APCI-MSn/DS will be the only instrument of its kind at the Homewood Campus of the Johns Hopkins University and will be fully accessible to research groups in all divisions of the University. Proposed research requiring access to the spectrometer extends from molecular biology and protein chemistry to materials science.